GA is a rare, blinding, chorioretinal degeneration inherited as an autosomal recessive trait. Visual symptoms include myopia and reduced night vision in the first decade, constriction of the visual fields and onset of posterior subcapsular cataracts in the second decade with continued contraction of the visual fields leading to blindness in the fourth to sixth decade. In childhood, the ocular fundus develops sharply demarcated, circular areas of chorioretinal degeneration in teh midperiphery. These lesions enlarge coalesce and extend towards the osterior pole and, by the fifth or sixth decade, there is complete chorioretinal degeneration. The purpose of this study is: To continue long-term evaluation of the efficacy of an arginine-restricted diet as therapy for the retinal degenration characteristic of GA. To compare the clinical, metabolic and biochemical features of GA patients with their molecular defects at OAT locus. To determine the metabolic phenotype of infants with GA.